With a boost from Russia and China, Secretary of State John Kerry mounted a major diplomatic push Friday to reach an interim nuclear deal with Iran, despite fierce opposition from Israel and uncertainty in Congress.

Kerry and his counterparts from Britain, France and Germany had arrived in Geneva with the talks at a critical stage following a full day of negotiations Thursday and said some obstacles remained in the way of any agreement offering reductions in sanctions for nuclear concessions.

Word that Russian Foreign Minister Sergey Lavrov and a Chinese deputy foreign minister also were headed to the talks provided fresh hope for at least an interim deal, perhaps on Saturday.

But Israeli Prime Minister Benjamin Netanyahu insisted any agreement in the making was a “bad deal” that he said gave Iran a pass by offering to lift sanctions for cosmetic concessions that Netanyahu said left intact Tehran’s nuclear weapons-making ability.

Late Friday, the White House announced that President Obama had called Netanyahu to give him an update on the talks and “underscored his strong commitment to preventing Iran from obtaining a nuclear weapon.”

The White house added that “The president and prime minister agreed to continue to stay in touch on this issue.”

Kerry tempered reports of progress, warning of “important gaps” that must be overcome in the elusive deal that would offer limited sanctions relief if Iran starts capping programs that could make atomic arms.

Asked about Netanyahu’s criticism, White House spokesman Josh Earnest said that “any critique of the deal is premature” before an agreement is reached.

Kerry arrived from Tel Aviv after meeting Netanyahu and trying to defuse concerns. Israel is strongly critical of any deal that even slightly lifts sanctions unless Iran is stripped of technology that can make nuclear arms.

Israel has been watching the talks with deep concern. It has frequently held out the prospect of military action against Iran should negotiations fail to reach the deal it seeks — a total shutdown of uranium enrichment and other nuclear programs that Tehran says are peaceful but that could be turned toward weapons.

“I understand the Iranians are walking around very satisfied in Geneva, as well they should because they got everything and paid nothing,” Netanyahu told reporters before meeting Kerry.

Many US lawmakers have the same demand as Netanyahu: They want enrichment to stop altogether in exchange for loosening sanctions.

“Any agreement that does not require the full and complete halting of the Iranian nuclear program is worse than no deal at all,” said House Majority Leader Eric Cantor.